Copper is an essential micronutrient in humans and the reactions catalyzed by copper-containing enzymes play a key role in cellular respiration, antioxidant defense, iron metabolism, connective tissue biosynthesis, pigment formation and neurotransmitter production. The long-term objective of these studies is to define the cellular and molecular determinants of human hepatocyte copper metabolism. The specific aim of this proposal is to elucidate the structure and function of the Wilson disease P-type ATPase. Previous studies in our laboratory have resulted in the cloning and characterization of the P-type ATPase encoded by the Wilson disease gene and the definition of the LEC rat as a bona fide model for this disorder. We now propose to extend these studies by defining the cellular localization, membrane structure and transport function of the Wilson ATPase. Using polyclonal antisera, available human cell lines, data on missense mutations, expression and cloning studies in yeast and in vitro hepatocyte reconstitution approaches we will dissect the mechanisms of copper transport by this protein. These studies should permit an understanding of the mechanisms of copper traffic within the hepatocyte as well as further definition of the molecular pathology of Wilson disease. Ultimately such data may provide novel approaches to the treatment of human disorders of copper metabolism and may offer new insights into the biological roles of copper in human nutrition and disease.